Blood pressure measuring device and a method of controlling the cuff pressure in a blood pressure measuring device

Abstract

For controlling the cuff pressure in a blood pressure measuring device, the volume flow between a pump for filling the cuff and a valve for emptying the cuff on the one hand and the cuff on the other hand is detected by a flow sensor whose output signal is integrated by means of an integration circuit for producing an actual volume value. A computer unit for controlling the pump and the valve produces the control signals on the basis of this volume value formed by integration as well as on the basis of at least one quantity representative of the pressure/volume dependence of the cuff pressure.

I claim: 
     
       1. A blood pressure measuring device comprising: a cuff which in use is wrapped around a part of the patient's body;   a pressure adjustment device for controlled filling and emptying of the cuff;   a flow sensor arranged between said pressure adjustment device and said cuff;   an integration means connected to be responsive to said flow sensor for producing a volume value; and   a control means for controlling the pressure adjustment device on the basis of the volume value produced by said integration means as well as on the basis of at least one quantity representative of a pressure/volume dependence of a cuff pressure on a cuff-filling volume.   
     
     
       2. A blood pressure measuring device according to claim 1, wherein the control means has a structural design of such a nature that it detects a gradient of the pressure/volume function on the basis of the respective actual volume values at two predetermined pressure values as the representative quantity. 
     
     
       3. A blood pressure measuring device according to claim 1, wherein the control means has a structural design of such a nature that it stores a pressure/volume function in the form of a plurality of actual volume values at a plurality of predetermined pressure values as a measured curve or measurement table. 
     
     
       4. A blood pressure measuring device according to claim 1, wherein the control means has a structural design of such a nature that it supplies a control signal to pressure generation device so that said pressure generation device fills the cuff until the pressure signal received from the pressure sensor reaches a maximum pressure value;   determines the quantity representative of a pressure/volume function;   calculates a target volume value for a respective next pressure step;   supplies to a valve the control signal for emptying the cuff until the actual volume value received from the integration means corresponds to the target volume value;   switches off the control signal for the valve so as to close said valve;   compares, when a predetermined period of time has elapsed after closing of the valve, the actual pressure with a target pressure of the present pressure step so as to detect a pressure deviation; and   takes into account the thus detected pressure deviation upon determining the target volume value for the next pressure step.   
     
     
       5. A blood pressure measuring device according to claim 1, wherein the flow sensor is provided with the following features: a flow area of reduced-diameter located between the cuff on one side and a pressure generation device as well as a valve on the other side;   a differential pressure sensor having its pressure inputs connected to the ends of the reduced-diameter flow area; and   a linearization means arranged downstream of said differential pressure sensor and having its output connected to the input of the integration means.   
     
     
       6. A blood pressure measuring device comprising: a cuff which in use is wrapped around a part of the patient's body;   a pressure generation device for filling or for venting the cuff;   a pressure sensor for producing a pressure signal;   a valve for controlled emptying of the cuff;   a flow sensor arranged between the cuff on the one side and the pressure generation device as well as the valve on the other side;   an integration means connected to be responsive to said flow sensor for producing a volume value and   a control means connected to the valve, the pressure sensor and the integration means and having a structural design of such a nature that it: (a) determines at least one quantity representative of a pressure/volume function on the basis of the pressure signal and the volume valve;   (b) calculates a target volume value on the basis of a target pressure value for a respective pressure step and on the basis of said quantity representative of the pressure/volume function; and   (c) supplies to the valve a control signal for emptying the cuff until an actual volume value received from the integration means corresponds to the calculated target volume value.     
     
     
       7. A blood pressure measuring device according to claim 6, wherein the control means has a structural design of such a nature that it detects a gradient of the pressure/volume function on the basis of the respective actual volume values at two predetermined pressure values as the representative quantity. 
     
     
       8. A blood pressure measuring device according to claim 6, wherein the control means has structural design of such a nature that it stores the pressure/volume function in the form of a plurality of actual volume values a plurality of predetermined pressure values as a measured curve or measurement table. 
     
     
       9. A blood pressure measuring device according to claim 6, wherein the control means has a structural design of such a nature that it supplies a control signal to the pressure generation device so that said pressure generation device will fill the cuff until the pressure signal received from the pressure sensor reaches a maximum pressure value;   determines the quantity representative of a pressure/volume function;   calculates the target volume value for a respective next pressure step;   supplies the valve control signal for emptying the cuff until the actual volume value received from the integration means corresponds to the target volume value;   switches off the control signal for the valve so as to close said valve;   compares, when a predetermined period of time has elapsed after closing of the valve, an actual pressure with the target pressure of the present pressure step so as to detect a pressure deviation; and   takes into account the thus detected pressure deviation upon determining the target volume value for the next pressure step.   
     
     
       10. A blood pressure measuring device according to claim 6, wherein the flow sensor is provided with the following features: a flow area of reduced-diameter located between the cuff on one side and the pressure generation device as well as the valve on the other side;   a differential pressure sensor having its pressure inputs connected to the ends of the reduced-diameter flow area; and   a linearization means arranged downstream of said differential pressure sensor and having its output connected to the input of the integration means.   
     
     
       11. A method of controlling cuff pressure in a blood pressure measuring device to be used on a patient, the blood pressure measuring device including: a cuff which in use is wrapped around a part of the patient's body;   a pressure adjustment device for controlled filling and emptying of the cuff;   a flow sensor connected between said pressure adjustment device and said cuff; and   an integration means responsive to said flow sensor for producing a volume value;   the method comprising: controlling said pressure adjustment device on the basis of the volume value produced by said integration means and on the basis of at least one quantity representative of a pressure/volume dependence of the cuff pressure on a cuff-filling volume.     
     
     
       12. A method according to claim 11 further including: calculating a gradient of pressure/volume function on the basis of the respective actual volume values at two predetermined pressure values.   
     
     
       13. A method according to claim 11 further including: storing in tabular form a pressure/volume function as plural actual volume values at a plurality of predetermined pressure values.   
     
     
       14. A method according to claim 11 further including: filling the cuff until a pressure signal received from the pressure sensor reaches a maximum pressure value;   determining the quantity representative of a pressure/volume function;   calculating a target volume value for respective next pressure step;   emptying the cuff until an actual volume value received from the integration means corresponds to the target volume value;   closing a valve;   comparing, when a predetermined period of time has elapsed after closing of the valve, the actual pressure with a target pressure of the present pressure step so as to detect a pressure deviation; and   taking into account the detected pressure deviation upon determining the target volume value for the next pressure step.   
     
     
       15. A method of controlling the cuff pressure in a blood pressure measuring device used on a patient, the blood pressure measuring device including: a cuff which in use is wrapped around a part of the patient's body;   a pressure generation device for filling or for venting the cuff;   a pressure sensor for producing a pressure signal;   a valve for controlled emptying of the cuff;   a flow sensor connected on one side between the cuff and the pressure generation device as well as the valve on its other side;   an integration means responsive to said flow sensor used for producing a volume value, and   a control means connected to the valve, the pressure sensor and the integration means,   said method comprising the steps of: determining at least one quantity representative of a pressure/volume function;   calculating a target volume value on the basis of a target pressure value for a respective pressure step; and   opening the valve to empty the cuff until an actual volume value received from the integration means corresponds to the calculated target volume value.     
     
     
       16. A method according to claim 15 further including: calculating a gradient of pressure/volume function on the basis of respective actual volume values at two predetermined pressure values.   
     
     
       17. A method according to claim 15 further including: storing in tabular form the pressure/volume function as plural actual volume values at a plurality of predetermined pressure values.   
     
     
       18. A method according to claim 15 further including: filling the cuff until the pressure signal received from the pressure sensor reaches a maximum pressure value;   determining the quantity representative of the pressure/volume function;   calculating the target volume value for the respective next pressure step;   emptying the cuff until the actual volume value received from the integration means corresponds to the target volume value;   closing the valve;   comparing, when a predetermined period of time has elapsed after closing of the valve, an actual pressure with the target pressure of the present pressure step so as to detect a pressure deviation; and   taking into account the detected pressure deviation upon determining the target volume value for the next pressure step.